1. Field of the Invention
The present invention relates to a sealed airtight container for housing an optical-semiconductor element. Specifically, it relates to the container for housing an optical-semiconductor amplifier and a light exciting source that include an optical element for which it is required that the amount of the current which flows at a current terminal part is twice or more than twice of the amount of the conventional element.
2. Description of the Prior Art
As shown in FIG. 1, a conventional sealed airtight container for the optical-semiconductors consists of a metal bottom plate 1, a side-frame 7 brazed on the bottom plate, ceramic terminal parts 3 attached to the side-frame, a sealing ring 5 brazed at the upper part, and a cover 11. The metal bottom plate is made of a cooper-tungsten (xe2x80x9cCuxe2x80x94Wxe2x80x9d) alloy, and has an area on which the optical-semiconductor element is set at the central part of its upper surface. The side-frames that surround the area setting the optical-semiconductor element are made of a iron-nickel-cobalt (xe2x80x9cFexe2x80x94Nixe2x80x94Coxe2x80x9d) alloy and have means to fix an optical fiber. The ceramic terminal part to which external lead wires 4 made of a Fexe2x80x94Nixe2x80x94Co alloy are connected has a metallized-wiring layer or wiring pattern 3d. The sealing ring is a metal frame that seals the optical-semiconductor airtight.
An optical-semiconductor element and a Peltier element are glued and fixed to the optical-semiconductor element mounting area of the metal bottom plate. Each electrode of the optical-semiconductor element is connected to the metallized-wiring layer connected to lead wires 4 through bonding wires (not shown). And an optical fiber (not shown) is joined to an optical fiber fixing ring 2 of the side-frame by brazing or Yttrium Aluminum Garnet (xe2x80x9cYAGxe2x80x9d) laser irradiation. Finally the upper surface of the seal ring is covered and sealed. The process described above is common to complete the optical-semiconductor module as a unit.
The ceramic terminal part is formed by sintering the two or more layers of a ceramic preform as shown in FIG. 3. Electrical conductivity between the inside and the outside of the sealed airtight container for the optical-semiconductor is acquired by printing the metallized-wiring layer on the surface of each preform before sintering. A heat resistant metal such as tungsten (xe2x80x9cWxe2x80x9d), molybdenum (xe2x80x9cMoxe2x80x9d), manganese (xe2x80x9cMnxe2x80x9d) is used for the metallizing.
A structure of a ceramic terminal part disclosed in Japanese Patent Application Laid-Open No. 145317/1999 is shown in FIGS. 2 and 3. The width of the metallized-wiring layer 3d on the ceramic surface shown in FIG. 2 is usually uniform in a direction from the front end to the distal end. In some of the sealed airtight containers for high frequency use, in order to avoid the reflective loss due to the mismatch of impedance, the width of the metallized-wiring layer 3d is made smaller partially in the direction from the front end toward the distal end.
An optical fiber fixing ring is prepared in the side-frame. Each electrode of the optical-semiconductor element glued and fixed on the metal bottom plate is connected through a bonding wire to the metallized-wiring layer that is connected to a lead wire. An optical fiber is fixed to the optical fiber fixing ring by YAG welding by irradiation of laser beams. In order to maintain airtightness in a package, a cover is fixed by electric-welding, and an optical-semiconductor module is completed.
With respect to the increased output of the laser diode (LD) used for the optical fiber amplifier or the light source for excitation, the drive current of the Peltier element which cools the LD element has come to need large current. With the structure of the conventional package shown in FIG. 1, since the resistance of the metallized-wiring layer of the ceramic terminal part was comparatively high, when current was passed, it was heated. Conventionally, the heat generation was such a degree as could be ignored since the current to pass was at most about 2A (Amperes). If the current to pass is at least twice of 2A, however, the heat generation cannot be disregarded. Namely, it has become impossible to ignore a temperature rise of the metallized-wiring layer as well as power consumption. With rise in temperature, the resistance of the metallized-wiring layer increases further. Consequently, the various problems had occurred such as a declining of an optical output due to a heated LD element, increased difficulty in the drive control of the Peltier element, or reduced reliability of the wiring layer.
In order to reduce the resistance of the wiring layer formed in the ceramic terminal part, the use of a metal whose electric conduction is superior to heat resistant metal such as tungsten can be considered. However, by this method, since the difference of the thermal expansion coefficient with ceramic becomes large, a crack occurs in the ceramic. Moreover, making the wiring layer thick and lowering the resistance are also considered. However, by this method, during the firing of the preform, an interstice occurs between the ceramic layers and an airtight seal is not possible. Furthermore, resistance can be reduced if the width of the wiring layer is thick. But, it is not possible to expand the width sufficiently because it would cause interference between the adjacent wiring layers, or otherwise the number of terminals decreases.
In light of the above-described conventional problems, an object of the present invention is to provide an sealed airtight container for optical-semiconductors which can carry a large current of more than the former and whose output is stable, lowering the resistance value of a metallized-wiring layer provided in a ceramic terminal part and thereby reducing the heat generation of a wiring part and maintaining a small power consumption. The object of the present invention is also to provide an optical-semiconductor module using such a sealed airtight container.
This invention is related to a sealed airtight container for optical-semiconductors. And in the sealed airtight container for optical-semiconductors, the width of the exposed electrode part provided in the ceramic terminal part is enlarged, and the exposed electrode part is connected to the wiring part provided in the ceramic terminal part, and the width of the wiring part is equal to the enlarged width of the electrode part.
Furthermore, there are the following means to reduce the electrical resistance further in the sealed airtight container in this invention. The first means to reduce the electrical resistance further is laminating two or more layers of the wiring parts that are separated by the ceramic layer. The second means is pasting the silver brazing alloy on the exposed electrode part. The third means is laminating the Cu layer on the exposed electrode part. The fourth means is laminating the external terminal on the exposed electrode part including the area where the width of the electrode part is made large.
The sealed airtight container for the optical-semiconductor with a small heat generation in the wiring pattern part, a small power consumption and the optical-semiconductor module with a stable optical output can be obtained by lowering the resistance value of the wiring pattern prepared in the ceramic terminal part.